The present invention relates to an improved ergonomically friendly surface-treating tool in which a flat surface of a pad engages the surface of a workpiece for the purpose of abrading or polishing it and more particularly to an improved orbital sander.
By way of background, in operation, orbital sanders create forces at the sanding surface which are transmitted back to the operator's hand and arm through a lever which is the height of the orbital sander between the face of the sanding disc and the top of the casing at the vertical centerline of the sander. Therefore, if this height is as short as possible, the operator's effort in overcoming the forces produced at the face of the sanding disc are less than if the height was greater.
In orbital sanders it is desirable that, in addition for the height of the tool being as small as possible, the connection between the housing and the pad should be sufficiently flexible to permit good orbital action but it should also provide good columnar strength so that the pad will oscillate in a very close plane, that is, movement in a vertical direction should be limited as much as possible.
In prior orbital sanders there were various types of connections between the housing and pad. In one type, a central relatively soft rubber post connected the pad to the housing. While this provided sufficient orbital flexibility, it permitted the pad to move out of a desired plane. In another type, thin rigid plastic multi-columnar post units were located at the corners of the pad between the pad and the housing. These thin rigid post units provided good columnar stability so as to confine the pad to a desired plane, but they had to be relatively long so as to be sufficiently flexible laterally to provide good orbital action, thereby increasing the height of the sander.
In addition, in all prior orbital sanders, the abrasive dust enters the housing containing bearings which support the spindle which carries the pad, thereby shortening the bearing life and also causing the pad to operate out of its desired plane. This is especially pronounced in the type of orbital sanders using central vacuum systems wherein a high volume of air is drawn through the sander housing to carry away the abrasives and foreign particles. This causes eddy currents at the various sharp edges including the edges of the eccentric housing which contains the bearings which mount the spindle to which the pad is attached. Abrasives and foreign particles may thus enter the bearing area because they are sucked in to this area because of changes in positive and negative pressures due to the operation of the tool. One attempt to reduce the amount of foreign matter entering the bearing area is shown in U.S. Pat. No. 4,854,085 which utilized a triple seal. This approach did increase the bearing life to a certain degree. It is with overcoming the foregoing deficiencies of the prior art that the present invention is concerned.